The 29er trail bike has quickly become the most popular genre in the mountain bike industry, and for good reason, with the vast improvements in geometry "wagon-wheeled bikes," as they were once called by the haters have taken over both consumer demand as well as the majority of the race world. Transition has been at the forefront of the trend, helping to improve 29er geometry with the initial release of Speed Balanced Geometry, which combines long reach, short offset forks, slacker head angles and steeper seat tube angles to improve stability, maneuverability, and climbing.

Transition Sentinel 2020 Highlights

  • Full EPS molded carbon frame (front triangle, rear triangle, and rocker)
  • New, progressive suspension design
  • 148mm Boost dropout spacing
  • Stock rear travel 150mm with 62.5mm stroke shock
  • Downsize to 140mm rear travel with 57.5mm stroke shock
  • Enduro Max sealed bearings with bearing shields on main pivot
  • 44mm/56mm Press In Headset
  • Threaded bottom bracket
  • Molded rubber chainstay, seatstay & downtube protection
  • External rear brake cable routing
  • Water bottle storage inside the front triangle
  • Accessory mount on underside of toptube
  • 29-inch wheels with tire clearance up to 2.6-inches wide
  • Weight: 7.05 lbs frame with shock, Complete bike with SRAM GX - 31.1 lbs as tested
  • MSRP: $5499 GX-build (as tested), $3199 (frame only)

What's New For 2020?

For 2020, Transition's latest Sentinel builds on this philosophy of versatility by making changes that open the bikes appeal to a broader audience. By adding 10mm of travel to the front and rear, the latest Sentinel comes stock with 150mm rear travel and 160mm up front, but can also be set up as it was previously offered with 140mm of rear travel. Other pertinent updates include improved suspension kinematics, making for a more progressive suspension curve compared to previous versions.

Transition Sentinel Pricing and Build Packages

Available with three different build packages and also as a frame-only option. Prices range from $3,199 for frame-only and $4,499 USD up to $6,599 USD for complete bikes. The mid-level GX Scout build sells for $5,499 USD (as tested) and comes equipped with a full SRAM GX Eagle drivetrain, SRAM Code RSC brakes, Stans Flow S1 Team wheels, a RockShox Lyrik Ultimate RC2 fork and RockShox Super Deluxe Ultimate shock. Build packages are rounded out with handlebars and saddle from Transition's house brand, Anvl, along with Sensus grips and a massive 210mm (sizes large/XL) OneUp dropper post.

Available in two colors, the Sentinel's matte finish is subtle yet sleek and accentuates the frame's sexy lines.​

Transition Sentinel Geometry and Frame Details

Available sizes range from XS to XL. Our Large-sized Sentinel test bike features a 476mm reach and 631mm stack height. Other important frame geometry numbers include a 63.6-degree headtube angle, 76.9-degrees effective seat tube angle, and 1263mm wheelbase, and all sizes of the bike get 440mm chainstays.

"For sizing stuff, we focus more on the reach and stack first, the overall wheelbase and the seat tube angle then eventually "top tube length" length last. With the types of bikes we are building the standing position is critical for your interaction with the bike and the wheelbase is your contact patch and connection with the trail." explains Transition Product Manager, Sam Burkhardt "Of course the bar to saddle distance is a consideration, but it definitely comes after the other factors. We find there is a lot more leeway on what feels "right" in that seated distance depending on the rest of the geometry."

These geometry numbers are an indicator of the continuing trend to go longer, especially in the wheelbase, where the latest size large grows to 1263mm from 1247mm, though the effective top tube shrinks from 622mm to 613mm. These changes may seem minimal, but when combined they help to create more refined ride characteristics across the board. Have we reached that point where longer, lower, and slacker has reached a balance between amazing descending and enjoyable climbing?

Integrated frame protection keeps trail chatter to a minimum while Enduromax bearings keep the pivots moving quietly and freely with some proven reliability.​

210mm dropper posts are a surprisingly unassuming game-changer out on the trail.​

Continuing with the rider refined improvements, the latest Sentinel is designed to accommodate the growing need for longer dropper posts with a good deal of standover height and a shorter seat tube allowing for longer droppers in all sizes-120mm dropper on the XS, 150mm on a small, 180mm on a medium and up to a 210mm on the large and XL frames, big numbers for a 150mm 29er trail bike.

We were pleasantly impressed with the OneUp dropper post. It was simple to adjust and did its job with no hiccups over the course of our time on the bike. With a shifter-style 1x lever, it makes using the post unconscious and we found every bit of the post to be super user-friendly.

The Sentinel features a full carbon frame made from premium Japanese Toray fiber with a tailored blend of 24T and 30T materials to create the right balance of frame stiffness, strength, and impact toughness. A unique latex coated EPS molding process allows for sharper frame lines and tighter edge radius control with maximum strength to weight ratio and less wasted material.

Clean frame angles give the Sentinel it's stout, utilitarian look while Transition's matte color choice blends in with the natural surroundings. Our GX-build test bike was equipped with a 62.5mm stroke Rockshox Super Deluxe with 150mm of travel.​

To keep the bike clean and quiet, cable routing is mostly internal except for the externally routed rear brake cable making it more easily serviceable while a fully-guided derailleur cable routing through downtube and chainstay help make cable and housing replacement an easy chore. Transition's commitment to creating reliable and durable bikes is a testament to the team of employees and brand ambassadors providing continuous feedback.

The Sentinel's latest frame details include a threaded bottom bracket and a press-in cup headset to accommodate anglesets. Integrated rubber chainstay, seatstay, and downtube provide frame protection and keep trail chatter to a minimum. Frame pivot bearings are sealed Enduro Max bearings and ours have remained quiet and smooth thus far despite lots of dust and quite a few washes and wet trips of the back of the car.

Tire compatibility has also grown with the latest Sentinel frame and will accommodate up to a 29x2.6″ tire. You'll also notice that all frame sizes can accommodate a bottle cage and include additional gussets beneath the top tube to allow for added carrying capacity of things like tools or a pump, a nice touch, but we haven't used it yet. ISCG05 mounts also allow the option to run a chainguide setup.

On the Trail

A quick setup was a telling sign that this bike fit like a glove. A few quick cockpit adjustments and a little fiddling with the cable tension on the OneUp dropper post (which I've been extremely happy with). Suspension setup took a bit of tinkering to find my sweet spot aboard our Rockshox equipped test bike, I settled at 58psi in the Lyrik and 165psi in the Super Deluxe which translated to about 28% sag under my ~160lbs. If I were purchasing this bike, I think I'd spend the extra coin to upgrade to the Fox suspension option as it fits my personal suspension preferences a bit more.

Despite the Sentinel's long, low, and slack demeanor the bike climbed like a mountain goat thanks to the balanced geometry of Transition's Speed Balanced Geometry (SBG).​

Once out on the dirt, the Sentinel was like an old friend who had just returned from a life-changing experience at a Buddhist retreat center. Climbing was planted, efficient, and eerily enjoyable. Transitions SBG geometry, though mostly designed around descending, performs extremely well on the climbs. Rider weight is positioned is nicely centered in the middle of the bike giving the bike great maneuverability through tight, technical climbs while still being comfortable and efficient on those long fire road grinds.

I was extremely impressed with the SBG geometry when attempting some challenging, rocky climbing section of trail that I have about 25% luck with (mostly success on the e-bike). Aboard the Sentinel, they became like a fun puzzle challenge, scoping the line through the loose shale before attempting it with the right amount of momentum and gear choice. Due to it's long, low nature, it felt planted and stable even at super slow speeds and I was impressed with how easily it was coaxed through the technical ups with confidence and comfort.

Smashing through rocks is where the Sentinel seems most at home, but I was also pleasantly surprised how playful and nimble it felt on trails with less texture.​

Now that we have the climbing analysis out of the way, descending is where the Sentinel really ramped up the experience. After a flip of the lockout switch on the Super Deluxe and a couple clicks out on the Lyrik's low-speed compression dial, the Sentinel was ready to party. It felt surprisingly lively and playful despite the bikes 1263mm wheelbase. Every root and rock became a play feature as the bike begged for more speed.

Dropping into the chunky sections of trail became a fun game of looking for new lines and attempting to air over as much of the chunder as possible. Monster trucking is also an option on the Sentinel and as your energy levels wane, or if you're a rider that prefers to keep the wheels on the ground, the bike is happy to plow through anything you can throw at it. No matter how you ride, the Sentinel accentuates the experience. I reached new levels of fun on this bike.


Wow, the Sentinel truly packs it all into one rig. I've cleaned more techy climbing sections, felt more confident on blind trails, and had more fun riding the Sentinel than many previous bikes. The Sentinel's climbing characteristics may require a bit of readjustment if you're not accustomed to Transition's geometry, but once you find the sweet spot, this bike will most certainly leave you satiated as you clean more technical bits than you have on any other bike.

I'd say Transition found an optimal balance with the latest geometry numbers on the Sentinel. No matter where we took this bike it seemed to manage the terrain with confidence and stability, up or down. I'm not a big guy, at 5' 10" and 160ish pounds, the large size Sentinel fit me well and I was happy with the bikes comfort from all standpoints.But where you'll find it to be most at home is romping down the trail with a playful demeanor as it opens up a new perspective of riding creativity. If you're looking for a beast of a bike for a mix of trails and terrain that can still hold it's own when it's time to pedal bike to the top, the Sentinel is the bike for you.

Join the conversation: visit the Transition Sentinel 2.0 thread in our forums